Make Debug.Control.choice take a nonempty list

In the documentation for [Debug.Control.choice](https://package.elm-lang.org/packages/avh4/elm-debug-controls/latest/Debug-Control#choice) it says
> This will crash if you provide an empty list.

Why not change the type signature to `( String, Control a ) -> List ( String, Control a ) -> Control a` so that can never happen?

Start with the linked Debug.Control.choice documentation and locate the function's implementation and current type signature. Review how choices are constructed and used, then establish whether the proposed nonempty-list API is appropriate and ensure the empty-list case is no longer possible and the documentation matches the resulting behavior.

Written by the indexing model from the issue text.